She further chided Sanders for not being upfront about the costs of his ambitious overhauls of public services, including health care and higher education.

“I do think when you make proposals and you’re running for president, you should be held accountable for whether or not the numbers add up, and whether or not the plans are actually going to work,” she said.

In past encounters, Clinton has suggested that Sanders’ plan to put in place an entirely new health care system would endanger the progress made towards universal coverage through the Patient Protection and Affordable Care Act (PPACA). He has called the criticism absurd, saying that there would be no scenario in which the PPACA would be scrapped if he cannot achieve his “Medicare-for-all” vision.

As he has in past debates, Sanders highlighted the fact that governments in other western countries guarantee coverage to their citizens, while spending far less on health care overall. He suggested that reluctance to embrace a single-payer system was due to fear of taking on the insurance industry.

“What Secretary Clinton is saying is that we are not a country that has the courage to stand up to big money and do what has to be done for the working families of this country,” he said.

Despite the string of recent defeats, Clinton remains the clear frontrunner for the Democratic nomination, with a sizeable lead among delegates.

Unlike the race for the Republican nomination, which has included a number of “winner-take-all” contests, every Democratic primary and caucus has awarded delegates to the candidates based on the proportion of the vote they receive. As a result, Clinton has still picked up a fair share of the delegates even in the states she has lost. Polls also suggest she will win the upcoming primary in New York by a comfortable margin.